In many engines with fuel injection systems, it is desirable to supply liquid fuel to the injector or injectors at a pressure which varies so that it is constant relative to the intake manifold pressure of the combustion air. Both the combustion air pressure and the flow rate of fuel supplied to the engine varies with engine speed, load and other operating conditions.
Previously, a variety of fuel pressure regulators have been developed one of which is shown in U.S. Pat. No. 4,627,643. This regulator has a generally flat, flexible diaphragm disposed between two chambers and subjected to manifold pressure on one side and pressurized liquid fuel on the other side. The flow of fuel through an outlet from the fuel chamber is controlled by a valve assembly having a ball trapped in a cage carried by the diaphragm and yieldably urged by a compression spring received in the manifold pressure chamber into engagement with a seat encircling the outlet. The ball is retained in the cage so that it can shift slightly only laterally in a plane parallel to the diaphragm.
In use, these regulators do not achieve or maintain a uniform and constant differential fuel pressure. Rather, the differential fuel pressure varies with the rate of fuel flow and drops as fuel consumption increases. Furthermore, these prior devices have a significant delay in their response to rapid changes in intake manifold pressure and flow rate produced by rapid changes in engine load, demand or other operating conditions. At best, transient variations of the nominal output pressure of these prior regulators have been about three to four psi.